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Safety in Swellex

The challenge

To construct a relatively shallow, large tunnel under a water body in shale bedrock working from very small work sites without impacting adjacent airport operations.

"We chose Atlas Copco rock bolts because of the ease of installation and inflation; the immediate support, very little production time delay and peace of mind that the bolt is fully inflated and providing support. Additionally we were able to utilise the available pull test equipment and benefit from outstanding product support."

Joe Dimillo

Billy Bishop Toronto City

Located on the downtown Toronto harbor front, 125 ft underground, 35 ft below Lake Ontario, this project connects the Island airport to the mainland allowing pedestrians to commute with unrestricted access to the Billy Bishop Toronto City airport. Today a ferry service is available. The Billy Bishop Toronto City Airport Pedestrian Tunnel is unique, it is the only tunnel today that connects an island to the mainland using a walkway. Once completed, shaft elevators on main land side, island side will incline escalators bringing service into the 21st century.

Billy Bishop Toronto City

Technicore Underground Inc. is based out of Newmarket Ontario, a family owned and operated business, founded in 1997 by Tony DiMillo, Owner Director. Tony’s son Joey DiMillo, Project manager, has seen the project through from ground breaking with secant piles through to concrete pouring in the tunnel currently underway. The secant wall was supported by a combination of tie-backs and struts and walers for both the mainland and Island shafts. Rock bolting and mesh were installed as required to provide safe working conditions. The shale contained very little limestone. Strengths ranged from 80 to 100 MPa.

Atlas Copco sales representatives were on hand to make recommendations for drill hole diameter for the use of the Swellex bolts. Atlas Copco personnel completed onsite training on the Swellex bolts installation and inflation arm instruction using both the PSP 300RDP air operated pump and H1 hydraulic Swellex pumps. Part of the product offering was to train Technicore personnel in the use of our pull test equipment for both the PM12 and MN24 Swellex bolts.

Excavation was started from Surface with 15 m length secant piles thru overburden into bedrock to stabilise the shaft opening. Several rows of tie back anchors were installed for the remaining 13 m of shaft depth down to overall depth of 28 m on main land side.

The tunnel arch support, is a very unique design concept that Technicore developed for this project. With the use of twin tunnel boring machines the main tunnel roof consisted of seven, 2 metre in diameter, interlocking horizontal secant tunnels, drilled and filled with concrete. Swellex PM12 bolts by 1.2 m in length were installed in the above tunnels for temporary support prior to filling the secant tunnels with cement.

The main shaft undercut wall required the installation of 3.6 m PM12 Swellex bolts. The overall main tunnel dimensions required were 11 metres wide, 7.3 metres high and 183 meters long. Once the profile of the tunnel had been excavated, 5 rows of 3.6m long MN24 Swellex bolts were installed for ground support.

"We chose Atlas Copco rock bolts because of the ease of installation and inflation; the immediate support, very little production time delay and Peace of mind that the bolt is fully inflated and providing support. Additionally, we were able to utilise the available pull test equipment and benefit from oustanding product support."

Joe Dimillo

It takes many partners to complete such a project. Technicore is responsible for the mainland and island shaft excavations, the main tunnel excavation, ground support and building the final Concrete structure. Forms and concrete will be supplied by TecMix, which is Another division of the Technicore Group of Companies.

PCL Construction Canada are the General Contractor that will build the elevator shafts in the mainland and inclined escalators on the island. Forum is funding this project and Arup Tunnel Designers are the engineering
consultants responsible for the tunnel design. The tunnel is a PC3 project and is a design build. It’s the only one around, only tunnel that connects the mainland to the island using a moving walkway creating a better way to travel to and from the island airport.

Atlas Copco is proud to be part of this ground breaking moment and providing safe solutions for sustainability.